Air Conduction
Hearing threshold levels can be determined by presenting test
signals to the test subject with the included earphones (air
conduction – AC). The purpose of AC audiometry is to establish the
hearing sensitivity at various frequencies. The test can specify the
AC loss but cannot distinguish between abnormality in the
conductive mechanism and sensor neural mechanism.
Headset Placement:
Remove eye glasses and ear rings if possible and position
the headband directly over the top of the head. Place the
rubber cushions so that the diaphragms are aimed directly
at the opening into the ear canal. Pull down the yokes of
the phones and adjust for tight fit. If the cushions are not
tight to the ears, the test results may be false at lower
frequencies.
Background Noise:
Background noise can also produce false test results,
especially at lower frequencies. If necessary, the DD45 can
be equipped with noise excluding enclosures. Please
contact the distributor for more information.
Instruction of Subject:
Prior to hearing threshold level measurements, the
following instructions should be given. "You will now hear a
variety of pitches with various loudness levels. Please push
the signal button when you hear a tone and release the
button when you no longer hear it. If not using the response
button, ask the patient to “raise their left or right hand when
you hear the tone in the left or right ear".
Threshold Determination:
The test normally starts at 1000 Hz on the patient's better
ear with the L/R switch adjusted accordingly.
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